Net loss per share - Computation (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Numerator:
Net loss	$ (75,189)	$ (24,082)	$ (34,345)
Denominator:
Weighted-average shares used to compute net loss per share, diluted (in shares)	118,276,462	108,908,597	102,752,092
Weighted-average shares used to compute net loss per share, basic (in shares)	118,276,462	108,908,597	102,752,092
Net loss per share, diluted (in dollars per share)	$ (0.64)	$ (0.22)	$ (0.33)
Net loss per share, basic (in dollars per share)	$ (0.64)	$ (0.22)	$ (0.33)